Subgroups of alcoholics express selective impairments in cognitive functions that require reflection (monitoring and evaluative functions as well as operations that are under voluntary control that are used to allocate cognitive resources). In contrast, the elderly, and many types of neuropsychiatric disorder patients, are unimpaired in their ability to use reflective functions even though they may demonstrate other types of impairments in memory and attention. Drug and behavioral challenges are useful in delineating the types of cognitive impairments that are present in these different types of patients (i.e., a benzodiazepine challenge in detoxified alcoholics, stimulant and cholinergic drugs challenges in elderly normal volunteers and in Alzheimer~s disease patients, ketamine in schizophrenic patients and normal controls, and DHEA administration in depression).